1S93.J <So * [Hyatt. 
Ctetol()(;y,^ ok tiik Study ok Acquiimcd Characteristics. 
VVeisraanii and his supporters deny that ctetic or acquired 
characters are inheritable, bat it is safe to make the assertion 
that this will not be maintained by the students of bioplastology. 
Within the limits of my own experience in tracing the genetic 
relations of varieties and species of fossil cephalopods and other 
groups through geologic time, although I have tried to analyze 
the behavior of all kinds of characteristics, I have failed to find 
any sucii distinctions. If Weismann's theory is true it ouglit 
to be practicable to isolate in each type some class or classes of 
modifications that would be distinguished by the fact that they 
were not inherited. 
It is i^racticable to isolate inherited chara(!ters from new varia- 
tions which liave not become fixed in any phylum. Tt is also 
l)racticable to point out characters which are transient in varions 
ways a}»pearing in individuals but not in varieties, in sjjecies but 
not in genera, and so on. When one has by this system of 
exclusion arrived at tlie end of the list he finds that there is no 
class of characteristics which may be described as non-inherit- 
able. The new variations of any one horizon which can be iso- 
lated from inherited ones are not distinguishable in any way 
from others which occurred previously. Later in time these new 
variations in their turn become incorporated with the younger 
stages of descendants. Tlie transient characters of the zoon 
also do not differ in any way from others that are inherited in 
allied species, genera, etc. For example, the jjositiou of tlie 
siphuncle is so variable in some species of Nautiloidea that it is 
not ciiaracteristic of the species, in others of the same order it 
is invariable within a certain range, and finally in some genera it 
is invariable. In the Ammonoidea, derived from the same common 
stock as the N^autiloidea, this organ attains a fixed structure and 
is invariably ventral from the Devonian to the end of the Creta- 
ceous, although in number of forms and genera the ammonoids 
far exceed the nautiloids. All characteristics, even those observ- 
able in some groups only in old age, are found in the adults of 
otiier groups, and finally in the young of the descendants of 
' Ktt|to's, something' acquired or gained. 
